Impacts of Metals on Infectious Diseases in Wildlife and Zoonotic Spillover

Climate change, mining activities, pollution and other human impacts on the natural environment cause significant changes in the concentrations and mixtures of metallic elements found in different ecosystems. Metals such as cadmium, copper, lead and mercury affect multiple aspects of host-pathogen interactions, influencing the risk of infectious diseases caused by various classes of pathogens. Notably, exposure to metals in doses and combinations toxic to the immune system can favor the dissemination of pathogens in natural environments, threatening the reproduction, well-being and survival of varied animal species. However, these problems remain neglected, since the influences of metals on infectious diseases are studied with a primary focus on human medicine. Therefore, this article aims to review the influence of metals/metalloids (e.g., arsenic, cadmium, chromium, copper, iron, lead, mercury, nickel, zinc) on infectious and parasitic diseases in animals living in natural environments. The potential impact of metals on the risk of zoonotic spillover events is also discussed. Metal pollution tends to increase as the demand for elements used in the manufacture of industrial products, batteries, and electronic devices increases globally. This problem can aggravate the biodiversity crisis and facilitate the emergence of infectious diseases. Considering the interconnections between pollution and immunity, measures to limit metal pollution are necessary to protect human health and biodiversity from the risks posed by pathogens. This review helps fill the gap in the literature regarding the connections between metal pollution and various aspects of infectious diseases.